Increasing SubArrays

You are given an array of N positive integers, A1, A2 ,…, AN.

Let’s denote by A[i, j] the subarray Ai, Ai+1 ,…, Aj.

Count pairs (i, j) such that 1 ≤ i ≤ j ≤ N and subarray A[i, j] is increasing. Return the value modulo 109 + 7.

Notes
- A subarray A1, A2 ,…, AN is increasing if Ai < Ai+1, for all 1 ≤ i < N.

For example,

A=[4, 5, 1, 2]

All subarrays of size 1 are increasing.

Subarrays A[1, 2], A[3, 4] of size 2 are increasing.

No subarray of size 3 and 4 is increasing.

So, total of 6 subarrays are increasing.

Interview Code Editor
371 successful submissions.
Click here to jump start your coding interview preparation